Why is Shaco getting major nerfs?

Because Riot hates Shaco. Always has, always will.

Yasuo, on the other hand, makes #LCSBIGPLAYS, so he'll always be OP, similar to Lee Sin.

Do you remember Season 2, before the shift from red and blue buff XP to the smaller minions in the camp?

Nunu, Shaco and Shyvana could just invade the enemy jungle, steal the buff from the enemy, get level 2 instantly and kill them or run away.

Now, after four long years we're going back to that, with red and blue buff being solo camps that get you to level 2 instantly. If Shaco remains as strong as he is, his invasions would decide games at level 1. The new jungle is very punishing to try and go through while you're down a level, down a buff, it's honestly just too strong and it's going to take a long time for people to get used to it. And Shaco would thrive in that confusion and make people just quit the game.

The same reason Yasuo has a ton of skins for a newer champ compared to some old champs in DESPERATE NEED of them. Because hundreds of thousands of weebs play Yasuo and spend money on him and like five people play Shaco. It used to be six, but that last guy got banned.

Because Yasuo's fan base is bigger

Remember Lee rework 2014 that got cancelled lmao

Looks like riot is intending to throw him in he dumpster until his VGUS like they did with poppy, urgot and other unhealthy champions.

Because shaco is being reworked right now and yasuo is not?

Also a few systemic changes help shaco, as enemy junglers will be easier to kill without SoA and control wards will not detect him like pinks do. The inclusion of "plants" is also probably slightly power positive since his boxes (which now last longer) can be placed to watch for or royally mess up an enemy attempt to use the plant)

Admittedly, the shaco changes seem a bit skewed towards AP, so if you prefer ad I see how the box and ult changes are less than thrilling.

I agree that yasuo is one of the more frustrating champions to face. I wish there was some way to make him less frustrating to face without removing his ability to lane mid, but frustrating machanics seem to be the most effective mechanics to enable a melee to function vs a ranged, especially in such a short lane.

The same reason Akali is getting nerfed, Riot doesn't want them to be playable, let alone viable.

Because Shaco isn't Zed. That simple.